The aim of this study was to characterize the clinical and genetic features of a 4-year-old female with merosin-deficient congenital muscular dystrophy type 1A (MDC1A). MDC1A is the most common form of congenital muscular dystrophy. MDC1A is caused by mutation of the laminin α-2 gene (LAMA2), localized to chromosome 6q22–23. Clinical presentation, as well as the results of neuro-imaging, electrophysiology and molecular genetic tests were used to evaluate a patient with MDC1A. The patient exhibited severe hypotonia and marked proximal weakness at 6 months of age, as well as delayed developmental milestones. The serum creatine kinase levels of the patient were elevated at 1,556 IU/l. Magnetic resonance imaging (MRI) showed that the white matter in the frontal, parietal, temporal and occipital lobes was abnormal with low signal intensities on T1-weighted images and high signal intensities on T2-weighted images; however, the cortex was normal. Sequencing of the 65 exons of the LAMA2 revealed a homozygous nonsense mutation in exon 50: a C>T exchange in nucleotide 7147 that resulted in a stop codon (Arg2383X stop). Molecular genetic testing is a reliable method for confirming a diagnosis of MDC1A. When a patient presents with severe congenital hypotonia, muscle weakness, high serum creatine kinase (CK) levels and white matter abnormalities, the evaluation may directly proceed to molecular genetic testing of the LAMA2 gene without performing a muscle biopsy.